Maldives is a small country without any conventional energy resources and
desperately needs alternative means to power their industry.
The work assesses the suitability of coconut oil as an alternative diesel fuel for the
use on the individual islands of the Maldives.
A study was carried out to identify the availability of resources relative to the energy
requirements of the country and coconuts became the most suitable candidate to
produce an alternative fuel for the existing diesel engines.
For the study on the long term effects of coconut oil and its derivatives (Methyl and
Ethyl Esters) a single cylinder direct injection Lister-Petter engine model AD I was
used. The engine was equipped for continous condition monitoring using a data
acquisition system. The system measures the in-cylinder and fuel injection pressures
relative to the crank angle. Also the cylinder and exhaust temperatures were measured
for all the fuels. Since the viscosity of the crude coconut oil is relatively high
compared to diesel a transesterification process was developed to reduce the viscosity
and this gave very good results. The physical and chemical properties of the fuels
were measured.
The engine was initially tested using a 20h test cycle with each fuel and this was
followed by a 200h test cycle on COIL. The engine performance was mapped in
terms of speed, load, volumetric fuel and air flow. In addition, exhaust gas analysis
was carried out to measure the regulated emissions. Tenax glass fibre, coconut
charcoal filters and dinitropheny1hydrazone tubes were used to sample the
unregulated emissions. The pressures and temperatures were continuously observed
and recorded at intervals. The ignition delay measurements showed that COIL and
COME had shorter ignition delay periods compared to diesel fuel.
During the tests engine lubricating oil was checked for possible fuel dilution. After
every 100 engine running hours, the engine was opened and physically inspected for
wear and damage, as well as for carbon and lacquer deposits. Pictures were taken of
the cylinder liner, piston top and cylinder head. The fuel injector was removed and
tested on the fuel injector test rig. The results were favourable and also the scanning
electron microscope measurements of the injector nozzle show that the deposits were
low when compared to diesel. A novel non-intrusive combustion chamber deposit
thickness measuring system was developed to measure the deposit thickness.
A separate rig was built using a similar type of fuel injection system as that on the
engine for fuel spray studies. Initially fuel spray photography was done using a high
speed camera to determine the pattern of the spray, spray penetration rate and the
cone angle for the three fuels. Once this was established a Malvern particle sizing
system was used to measure the droplet sizes for all fuels.
The results of the spray experiments helped to explain differences observed in the
engine performance for the different fuels. All the work carried out to date supports
the use of coconut oil as an alternative fuel for diesel engines in the Maldives.

Description:

A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.